Are you looking for recordings of particular instruments or vocal ranges? Use the library catalog's more search options feature to specify musical instrumentation. When you click on the box, a drop-down menu appears (as shown) with an amazing list of choices.

Oh, you play the harp? In addition to records, harpists can find books - like this one - to help with your sight-reading.

Ah, the vocalists in the crowd want to hear about selections for them -- here are glorious recordings of men's choruses, sopranos, and wonderful bass voices including those in Beethoven's only opera, Fidelio.